Biogeochemical Impact and Fate of Non-phosphorus Membrane Lipids in the Sargasso Sea

完整极性二酰基甘油（IP-DAGs）是构成细菌和真核细胞膜的脂肪酸承载脂质分子。因此，它们是浮游生物中最丰富的脂质分子之一，在海洋碳循环中发挥着重要作用。然而，直到最近，IP-DAGs的分子多样性知之甚少; IP-DAGs的结构一致性和特征几乎完全从其组成脂肪酸推断。 这些不含磷的IP-DAG在化学海洋学中基本上是未知的。相比之下，已经成为相当多研究的焦点的磷脂构成总IP-DAG的一小部分。 但是，我们仍然缺乏甚至粗略的了解非磷IP-DAGs的生化功能和地球化学归宿。鉴于这些分子是地球上最丰富的脂质分子之一，这代表了我们对海洋碳和磷循环的理解存在深刻而意想不到的空白。在这个项目中，伍兹霍尔海洋研究所的研究人员将对这些知之甚少的化合物展开开创性的研究。 他们的方法将由四个问题指导：（1）无磷脂质如何影响马尾藻海颗粒有机物的C：N：P变化？ (2)表层沃茨中磷脂和非磷脂类的相对降解率是多少？ (3)哪些微生物群利用来自不同IP-DAG的碳和磷？ (4)不同的IP-DAG对颗粒有机物向深海输出的相对贡献是什么？这些问题将通过使用先进的HPLC/MS分析和新的同位素示踪方法，结合长期存在的测量浮游生物C：N：P和确定有机分子降解率的方法来回答。 研究小组将确定这些新认识的硫脂和甜菜碱脂质分子是否是浮游植物在营养胁迫下影响灵活的C：N：P化学计量的定量重要生化选择。他们还将阐明降解速率，微生物命运以及IP-DAG中碳和磷的出口潜力。这将揭示这些分子在这些元素的循环中的更广泛的作用。更广泛的影响：该项目包含专门设计的组件，以满足NSF的标准，即“在促进教学，培训和学习的同时促进发现和理解”。“该项目将支持培训一名研究生和博士后研究员。此外，研究小组将与伍兹霍尔的非营利性Zephyr基金会合作，根据该小组的研究设计教育“单元”，这些单元将为6 - 12年级的学生量身定制。该基金会将介绍这些单位作为他们的动手海洋科学实地考察系列的一部分，每年提供给200多名学生和他们的老师。该基金会非常适合这一目的，吸引了来自马萨诸塞州和罗得岛的学校团体，包括代表性不足和弱势群体，如波士顿和新贝德福德的市中心计划。

Intact polar diacyglycerols (IP-DAGs) are the fatty-acid bearing lipid molecules that compose bacterial and eukaryotic cell membranes. As such, they are one of the most abundant classes of lipid molecules in plankton, and play a major role in the marine carbon cycle. However, until very recently, the molecular diversity of IP-DAGs was poorly understood; the structural identity and characteristics of IP-DAGs were inferred almost exclusively from their constituent fatty acids. These non-phosphorus containing IP-DAGs were largely unknown to chemical oceanography. In contrast, phospholipids, which have been the focus of considerable research, compose a disproportionally small fraction of total IP-DAGs. But we still lack even a cursory understanding of biochemical functions and geochemical fates of non-phosphorus IP-DAGs. Given that these molecules are among the most abundant lipid molecules on the planet, this represents a profound and unexpected gap in our understanding the marine carbon and phosphorus cycles.In this project, researchers at the Woods Hole Oceanographic Institution will launch a pioneering study of these poorly understood compounds. Their approach will be guided by four questions: (1) How do non-phosphorus lipids contribute to variations in the C:N:P of particulate organic matter in the Sargasso Sea? (2) What are the relative degradation rates of phospholipids and non-phosphorus lipids in surface waters? (3) Which groups of microbes utilize the carbon and phosphorus from different IP-DAGs? (4) What are the relative contributions of different IP-DAGs to particulate organic matter export to the deep-sea? These questions will be answered by using sophisticated HPLC/MS analyses and novel isotope tracing approaches in conjunction with long-standing methods for measuring the C:N:P of plankton and determining the degradation rates of organic molecules. The research team will establish whether these newly-recognized sulfolipids and betaine lipids molecules are a quantitatively important biochemical option for phytoplankton to affect flexible C:N:P stoichiometry in the face of nutrient stress. They will also elucidate the degradation rate, microbial fate, and export potential of the carbon and phosphorus from IP-DAGs. This will shed new light on the broader roles of these molecules in the cycling of these elements by the planktonic community. Broader impacts: This project contains components that are specifically designed to meet the NSF criteria for "advancing discovery and understanding while promoting teaching, training and learning." The project will support the training of a graduate student and postdoctoral fellow. In addition, the research team will work with the non-profit Zephyr Foundation in Woods Hole to design educational 'units' based on the team's research that will be tailored to student in grades 6 - 12. The Foundation will present these units as part of their hands-on marine science field trip series that is delivered to over 200 students and their teachers per year. The Foundation is ideally suited for this purpose and attracts school groups from Massachusetts and Rhode Island, including underrepresented and disadvantaged groups such as inner-city programs from Boston and New Bedford.